Manufacture of practically endless extrusion products



March 20, 1956 E. EMMERICH 2,733,373

MANUFACTURE OF PRACTICALLY ENDLESS EXTRUSION PRODUCTS Filed Dec. 17,1954 2 Sheets-Sheet l it, 0 11mm? 1 fiebdae March 20, 1956 E. EMMERICH2,738,373

MANUFACTURE OF PRACTICALLY ENDLESS EXTRUSION PRODUCTS Filed Dec. 17.1954 2 Sheets-Sheet 2 United States Patent MANUFACTURE OF PRACTICALLYENDLESS EXTRUSION PRODUCTS Ernst Emmerich, Koln-Eruck, Germany, assignorto Schloemann Aktiengesellschaft, Dusseldorf, arm-any Practicallyendless extruded rods, tubes, cable sheaths and the like can bemanufactured upon ,discontinuously working extrusion presses, with theinterposition, during the pressing, of pauses in which the press ram isretracted and fresh material is inserted, in the form of a billet forexample. In this manner, also, cables can be sheathed with lead oraluminium.

This process has however the disadvantage that'at intervals upon theextruded product so produced sofcalled bamboo rings appear, in theregion of which the thickness of the product is reduced, or at least theextruded material exhibits a structure different from that of theremainder. These bamboo rings occur from time to time when one stroke ofthe press is terminated and the press ram is retracted to enable freshmaterial for extrusion to be introduced; for at this moment the pressurebearing upon the material diminishes, and this is .what leads to theformation of the so-called bamboo rings.

The disadvantages of these bamboo rings become particularly noticeablein cable sheaths, because in practice cables have to be of indefinitelength, and furthermore have to be wound upon a drum or the like. Theposition of the bamboo ring therefore represents a weakening of thecable sheath, which is felt to beparticularly disadvantageous when thecable sheath is repeatedly bent. just at this point. Severe bendingstresses are therefore more liable to lead to breakage at the positionof the bamboo ring than equal stresses would be at any other point ofthe cable sheath.

The object of this invention is to obviate or reduce the disadvantagesof the bamboo rings, and the invention consists in imparting to thebamboo ring that is formed between two strokes of the press, by means ofsuitably-constructed tools, a formation which lies outside any planewhich is perpendicular to the axis of the press. The barnboo ring uponthe tube or the cable sheath may for example be given an ellipticalform. It will then lie in a plane which is inclined to the axis of thecable. A construction also appears advantageous in which the bamboo ringrepresents upon the cable sheath or the tube a double sinusoidal line.

The tools for carrying out this process are characterised by the factthat the rod-forming zone of the die is wholly or partly oblique to anyplane perpendicular to the axis of the press. In the case of toolsconsisting of a mandrel and a die for the production of hollowextrusion-press products, preferably of tubes and cable sheaths, therodforming gap is preferably so constructed that it is inclined to theaxis of the press. In order to obtain the abovementioned sinusoidalbamboo line, tools may also be employed in which the rod-forming gap hasthe shape of a sine curve marked upon a cylinder.

The formation of the bamboo ring according to the invention is also, inmany kinds of cables, of electrotechnical importance, particularly inso-called concentric high-frequency cables. In these the aluminiumsheath serves at the same time as a return conductor. At rather highfrequencies the circular bamboo ring of ,the usual shape then has a veryprejudicial efiect as a point of reflection. This is obviated, or atleast diminished, if the bamboo ring is produced according to theprocess of this application, that is, if it no longer lies in a planeperpendicular to the axis of the sheath.

Theinvention is illustrated by way of example in the accompanyingdrawings, in which:

Figures 1 and 3 show developed tube peripheries;

Figures 2 and 4 show outside views of the tubes; and

Figures 5, 6 and 7 show in axial section tools that may be employed forputting the invention into practice.

Figure 1 shows a developed tube periphery 1, in which the bamboo ring 2is of sinusoidal shape. This shape of the bamboo ring obviates the riskof breakage of the sheath 1. Figure 2 shows the same cable sheath inelevation. Figure 3 shows the development of a periphery 3, which isrepresented in elevation in Figure 4. The bamboo ring 4 is here locatedin a plane which is at an inclination to the axis of the sheath 3.

Figure 5 shows a chamber die consisting of a die memher 6; and an uppermember 7. These two members are undisplaceable relatively to one anotherowing to centering rings 8. The die 6 has an elliptical edge 9, whichlies in a plane that is not perpendicular to the axis of the press. Themandrel tip 10 has a corresponding elliptical shape, so that between thedie and the mandrel there is a gap 11 of substantially constant breadth,'the plane of which is inclined to the axis of the press. This gaptherefore forms a bamboo ring of the shape shown in Figure 4.

Figure 6 shows a die 12 and a mandrel tip 13. This mandrel tip may bedisplaceable and adjustable in the direction of pressing realtively tothe die 12, for the pur pose of producing sheaths of differentthicknesses. Such tools are employed on an ordinary tube-extruding presswith an adjustable mandrel. Since the mandrel 13 is hollow, a cable canbe sheathed with tools of this kind.

Finally Figure 7 shows a tool with which bamboo rings substantially asshown in Figures 1 and 2 can be produced. The mandrel tip 13a has here,like the die 1201, a sinusoidal edge bounding the gap 14.

The invention can also obviously be carried out with differentlyconstructed tools, for instance tools in which the mandrel tip is ofV-shaped construction, and the die is adapted to this V-shape.

I claim:

1. A method for the production of practically endless extruded rods,tubes, cable sheaths and the like upon discontinuously working extrusionpresses, characterised by the feature that to the so-called bamboo ringthat forms between two strokes of the press there is imparted a shapewhich lies outside any plane perpendicular to the extrusion axis.

2. A tool for the production of practically endless extruded rods,tubes, cable sheaths and the like upon discontinuously working extrusionpresses by the method claimed in claim 1, characterised by the featurethat the rod-forming zone of the die is at least partly oblique to anyplane perpendicular to the axis of the press.

3. A tool as claimed in claim 2 for the production of hollowextrusion-press products, preferably tubes and cable sheaths,characterised by the provision of a mandrel and a die, separated fromone another by a rod-forming gap situated at an inclination to the axisof the press.

4. A tool as claimed in claim 2 for the production of tubes and cablesheaths, characterised by the provision of a mandrel and a die,separated from one another by a rod-forming gap which has the form of asinusoidal curve marked upon a cylinder.

No references cited.

